1. Field of the Invention
The present invention relates to a pipe coupling device, and more specifically to a pipe coupling device that joins and connects pipes from which corroded or damaged portions are cut out.
2. Description of the Related Art
Piping work is generally carried out by cutting a plurality of pipes having various lengths and connecting the cut pipes together to form pipelines according to installation environments. Pipe coupling devices are used for the limited length of pipes and the necessity to change the position of pipelines during piping work.
Main applications of pipes are water supply and drainage lines for the transport of water and hydraulic lines for the transport of fluids such as oil. In addition, pipes are used to transport gases and various raw materials such as powders.
When it is intended to produce a long transport line, a number of coupling sites are required in the middle of the transport line due to the limited length of pipes. Coupling structures capable of maintaining hermetic sealing of the transport line are also required at the coupling sites to prevent leakage from the transport line.
In many cases, pipes tend to corrode by impurities settled therein or are damaged by external impact. In serious cases, it is necessary to remove the corroded or damaged portions from the pipes by cutting. Pipe coupling devices are often used to connect the pipes after cutting.
A pipe coupling device having a length of 6 cm to 7 cm is currently used to connect pipes from which portions having a width of 2-3 cm are cut out.
FIG. 1 proposes a prior art pipe coupling device. In the pipe coupling device, internally threaded portions are formed at both ends of a joint pipe 6, an inclined plane 10 extends from each of the internally threaded portions toward the central portion of the inner circumferential surface, a packing member 5 and a washer 4 are inserted into each of the inclined planes 10, and fixing bolts 3c are screwed into the joint pipe 6 to connect pipes 1. A central portion 13, a parallel threaded portion 11 extending from one side of the central portion 13 and a tapered threaded portion 12 extending from the other side of the central portion 13 form the outer circumferential surface of the fixing bolt 3. The central portion 13 is polyhedral, which enables the use of a suitable tool. When the parallel threaded portion 11 is screwed into the joint pipe 6, the packing member 5 is pressurized and fitted between the inner circumferential surface of the joint pipe 6 and the outer circumferential surface of the pipe 1 to maintain hermetic sealing of the pipes 1. A plurality of cut-away portions 7 are formed in the axial direction. When the inner circumferential surface of the tapered threaded portion 12 having an outer circumferential surface, whose outer diameter decreases toward the front portion, formed with a tapered screw is screwed into a tightening nut 2, the inner circumferential surface of the tapered threaded portion 12 is curved toward the outer circumferential surface of the pipe 1 and is fixedly secured to the pipe 1.
However, the prior art pipe coupling device connects pipes from which only portions containing settled impurities are cut out within a length range without departing from an allowable tolerance range of a currently available pipe coupling device. Thus, the periphery of the settled portions is liable to corrode.
It is difficult to connect pipes from which only small portions are cut out because pipes inserted into both ends of the pipe coupling device have the same insertion depth.
Further, in the case where the insertion depths of pipes inserted into both ends of the pipe coupling device are not exactly known, asymmetric insertion lengths of the pipes cause poor hermetic sealing, leading to water leakage.
Further, coupling errors may occur because the time when the coupling is finished is unknown.
The use of metal materials in order to improve the heat resistance and strength of the coupled portions entails considerable manufacturing costs.